1. Field of the Invention
The invention relates to a method for adaptively driving data transmission, and particularly relates to a method for adaptively driving data transmission of a high-speed input/output system and a communication device using the same.
2. Description of Related Art
The current trend of signal (or data) transmission between electronic devices or within an electronic device is directed to high-speed transmission. In order to achieve high-speed transmission, transmission of most input/output (I/O) systems use differential signals for data transmission to mitigate the noise interference generated during the high-speed signal transmission and simultaneously reduce the influence of its data transmission on other electric circuits.
FIG. 1A is a schematic diagram illustrating a high-speed input/output system. In a high-speed I/O system 10 illustrated in FIG. 1, a transceiver 110 and another transceiver 130 transmit and receive data signals through a transmission line 120. The transceiver 110 has a transmitting end TX and a receiving end RX in pair, corresponding to a receiving end RX and a transmitting end TX in pair of the transceiver 130. The transceiver 110 drives data as an output signal after receiving the data to be transmitted (e.g., digital signal), and transmits the output signal to the transceiver 130 through the transmission line 120.
During the high-speed signal transmission, the transceiver 110 usually generates a sequence of transmitting signal TS based on the output signal. In the transmitting signal TS, the transceiver 110 does not change the driven amplitude level when the data signals of “0” and “1” are transmitted in turn continuously. However, when a plurality of data signals of “0” or “1” are transmitted continuously, the transceiver 110 may de-emphasize or pre-emphasize the driven amplitude level. Taking a partial transmission signal 140 in FIGS. 1A and 1B as an example for illustration, the partial transmission signal 140 illustrates a de-emphasized amplitude level. Without de-emphasis or pre-emphasis applied on the driven amplitude level, when switching back to the opposite state during the high speed signal transmission (e.g., continuous transmission of data signals of “1” followed by switching back to transmission of data signal of “0”), the transmitting signal is likely not to be switched back in time, rendering floating effect of amplitude level of the signal received at the receiving end. Floating of amplitude level of the signal makes the transceiver 130 at the receiving end unable to identify the last bit or last few bits of the data signals of “0” or “1” that are sent continuously.
FIG. 1B illustrates a tolerable range of de-emphasis level and pre-emphasis level. In FIG. 1B, an amplitude level line NL is usually a communication standard followed by the high-speed I/O system 10 (e.g., USB, SATA, PCI Express standard, and so like.) Waveforms 141 and 142 respectively represent the tolerable range for the amplitude level line NL which may be de-emphasized and pre-emphasized, for example, ±6 dB.
Usually, the communication standard only specifies the transmitting end to drive in a fixed way, which uses a fixed amplitude level and apple fixed de-emphasis or fixed pre-emphasis of the amplitude level on the driven transmission signals. However, channel fading effects of the transmission line are prone to the influence of the length of the transmission line and the surrounding electric circuits. For example, the transmission line used by the high-speed I/O system 10 may a bus circuit of a printed circuit board in addition to the wires for data transmission. There may be a plurality of combinations of the printed circuit boards and wires for data transmission, which may result in a plurality of possible lengths of the transmission lines. If a fixed driving is applied on the data transmission, link failure between two device ends of the high-speed I/O system 10 may easily occur.